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Chapter 5 Practice Paper: Molecular Genetics — question paper

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QQ/S4BI/CH5

Secondary 4 · Biology (G2 / G3)

Chapter 5 Practice Paper

Molecular Genetics

Duration: 40 minutes
Total: 30 marks
Name:
Class:
Register No.:
Date:

READ THESE INSTRUCTIONS FIRST

  • Write your name, class and register number in the spaces at the top of this page.
  • Answer all questions.
  • Give numerical answers correct to 3 significant figures unless stated otherwise.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total number of marks for this paper is 30.

Original practice material written for the MOE Biology syllabus. It is not an official MOE or school examination paper. DNA, genes and chromosomes; nucleotide and double-helix structure; complementary base pairing; genes coding polypeptides; gene transfer; transgenic organisms and insulin production; benefits and ethics of genetic engineering.

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose the one correct answer for each question.

  1. 1

    Which statement about the structure of DNA is correct?

    1. AIt is a single strand of amino acids.
    2. BIt is a double helix of two nucleotide strands with paired bases inside.
    3. CIt is a branched chain of glucose units.
    4. DIt is a protein coiled around genes.
    ( )
  2. 2

    One DNA strand segment reads A–C–G–T. Its complementary segment is

    1. AT–G–C–A
    2. BA–C–G–T
    3. CC–G–T–A
    4. DU–G–C–A
    ( )
  3. 3

    A gene codes for

    1. Aone polypeptide
    2. Bone chromosome
    3. Cone fat molecule
    4. Done entire organ
    ( )
  4. 4

    A DNA molecule contains 250 bases, of which 50 are cytosine. The number of adenine bases is

    1. A25
    2. B50
    3. C75
    4. D100
    ( )
  5. 5

    Bacteria engineered to carry the human insulin gene produce insulin because

    1. Abacteria already make insulin naturally
    2. Bthe genetic code is universal, so bacteria read the human gene correctly
    3. Chuman chromosomes are added to the bacteria
    4. Dinsulin is assembled directly from DNA without a code
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 1

    DNA is often drawn as a ladder twisted into a spiral.

    1. (a)

      Name the three parts of a DNA nucleotide and state which parts form the ladder’s side rails.

      [2]
    2. (b)

      One strand reads A–T–G–C–C–A. Write the sequence of the complementary strand.

      [2]
    3. (c)

      A sample has 60 bases, of which 15 are adenine. Calculate the percentage of guanine in the sample.

      guanine =%[2]
  2. 2

    Genes are the units of inheritance, passed from parents to offspring.

    1. (a)

      Define a gene and state what it codes for.

      [2]
    2. (b)

      Explain how the base sequence of a gene determines the sequence of amino acids in its polypeptide.

      [3]
    3. (c)

      A polypeptide is 120 amino acids long. Calculate the minimum number of bases its gene must contain.

      bases =bases[2]
  3. 3

    Before biotechnology, insulin for diabetic patients was extracted from the pancreases of slaughtered animals. Today, bacteria carrying the human insulin gene produce the hormone in fermenters.

    1. (a)

      Describe how the human insulin gene is introduced into bacteria.

      [3]
    2. (b)

      Explain why bacterial cells can produce a protein normally made by human cells.

      [2]
    3. (c)

      State one benefit and one ethical consideration of this use of genetic engineering.

      [2]

— End of paper —